1. Field of the Invention
The present invention relates to a lens barrel for use in, for example, a digital still camera, a video camera, and an interchangeable lens, and in particular, to a lens barrel that manually performs a zooming operation.
2. Description of the Related Art
There exist rear-focusing lens barrels that include a focus lens disposed at an image-plane side to a zoom lens and configured to correct image-plane variations occurring with motion of the zoom lens and to perform a focusing operation.
One example of such lens barrels is a lens barrel that performs zooming by a manual operation (manual zoom operation) and focusing by an electric operation (automatic focus operation) to improve a shooting operation.
One such example is a lens barrel disclosed in Japanese Patent No. 03514245, which includes peripheral members disposed in a range of motion of a focus moving frame. In this lens barrel, a zoom moving frame is subjected to a zooming operation performed manually at high speed.
During this operation, an urging member is configured to absorb interference occurring between the focus moving frame and other peripheral members. The focus moving frame is coupled via a cam to a zoom driving member for moving the zoom moving frame along the optical axis. The zoom driving member is rotated, thereby moving the focus moving frame along the optical axis.
A focusing operation is carried out by movement of a holding member that holds the focus lens along the optical axis using a focus driving member attached on the focus moving frame. Accordingly, the focusing operation is independent of the operation of the zoom driving member.
The urging member urges the focus-lens holding member and the zoom driving member along the optical axis in a direction that separates both members away from each other while being positioned between both members. The urging direction is a direction that reduces rattling of a screw mechanism that screws the focus-lens holding member along the optical axis.
However, for the lens barrel disclosed in the above-mentioned patent document, because the focus-lens holding member and the zoom driving member are urged in a direction that separates both members away from each other, the focus driving member undergoes resistance of the urging member, in addition to resistance of the focus lens itself.
Therefore, it is necessary for the focus driving member to normally have a driving force that overcomes the total of the resistance of the focus lens itself and the resistance of the urging member.
Additionally, the coupling structure between the focus moving frame and the zoom driving member via a cam results in an increases in the size of the lens barrel caused by an increase in the size of the cam ring, mounting of a component required for the cam coupling, and a complicated structure of components.